Grinding apparatus



Sept. 28, 1965 E. o. L. WALLEN GRINDING APPARATUS e Sheets- Sheet 1 Filed Feb. 15, 1962 Sept. 28, 1965 E. o. L. WALLEN 3,208,679

GRINDING APPARATUS Filed Feb. 15, 1962 e Sheets-Sheet 2 Sept. 8, 1965 E. o. L. WALLEN 3,208,679

GRINDING APPARATUS Filed Feb. 15, 1962 6 Sheets-Sheet 3 Sept. 28, 1965 E. o. L. WALLEN 3,208,679

GRINDING APPARATUS Filed Feb. 15, 1962 6 Sheets-Sheet 4 FIG.7

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GRINDING APPARATUS Filed Feb. 15, 1962 6 Sheets-Sheet 6 FIG.9

United States Patent 3,208,679 GRINDING APPARATUS Emil Olof Lennart Walln, Stockholm, Sweden, assignor to Grubbens & Co. AB, Stockholm, Sweden, a Swedish joint-stock company Filed Feb. 15, 1962, Ser. No. 173,474 Claims priority, application Sweden, Feb. 22, 1961, 1,87 3/ 61 14 Claims. (Cl. 241-261) This invention relates to a grinding apparatus or homogenizer comprising grinding members adapted for relative rotary movement and having, for example, flat, conical or cylindrical grinding surfaces, each of the said surfaces being provided with one or a plurality of lines of depressions arranged in circles having the axis of rotation as their center and located on one or several planes at a right angle to the axis of rotation, the said lines of depressions being displaced in relation to one another in such a manner, that at least one wall to the side of at least one line of depressions in one grinding surface is located directly in front of some part of the line or lines of depressions in the opposite grinding surface.

Grinding surfaces provided with continuous grooves or bars extending along a line angular with the radius or radially to flat grinding surfaces or along a generatrix or a line angular with the generatrix in cylindrical and conical grinding surfaces are already known. Grinding apparatus comprising grinding surfaces of the aforesaid type include, however, the disadvantage that part of the material to be ground is advanced in untreated state in the grooves or in the channels between the bars without being contacted by the other grinding surface. Attempts were made to overcome these disadvantages by inserting low dams or stop bars in the grooves and channels or by making the channels more shallow.

Grinding surfaces of the aforesaid design are usually located at a relatively small distance from one another, the spacing sometimes being of such a small magnitude that the grinding surfaces due to play in the grinding shaft bearing come into contact with one another as soon as the supply of the material to be ground is interrupted; which contact may cause destruction of the grinding apparatus.

In another type of grinding surfaces, the surfaces are serrated in various patterns with the main purpose of catching and possibly breaking the material rolled or kneaded between the grinding surfaces. There is a great risk with this type of grinding surfaces that the material to be ground passes through one sector of the grinding surfaces too rapidly (channelling) and through other sectors too slowly (displacement and overgrinding).

Grinding surfaces of still different type comprise pins or jags secured alternately to the one or the other grinding surface: In such a case, the material to be ground is passed alternately along an inoperative or counterrotary row of pins and thereafter along a row of pins rotating in the same direction, wherebly the material is crushed. There is the risk of channelling and displacement even in this type of grinding surfaces.

In certain types of commercially available grinding apparatus, it is the object of the construction to direct all of the material to be ground past and across the active grinding surfaces or edges. In disc-shaped grinding members, the material is caused to pass axially through the two grinding discs which are perforated or in another manner provided with openings. In cylindrically shaped grinding surfaces according to this construction, the material to be ground is caused to pass radially through the cylinder jackets. This type of grinding apparatus includes the disadvantage that the material to be round passes too rapidly along the grinding surfaces.

The aforesaid drawbacks have now proved to be removable to a high degree and an improved grinding effect is obtainable by a grinding apparatus according to the invention which is characterized in that at least one wall to the side of a row of depressions in one grinding surface is elevated and projects into opposite depressions in the opposite grinding surface, the walls between the said depressions being provided with recesses adjusted to the said elevations. The said elevations may be perforated or provided with jags or slots etc., either to the entire height of the elevations or to a part thereof. The elevations are preferably wider at their base. The bottom in the depressions of the grinding surface located directly opposite the elevations are advantageously provided with holes of like or varying shape, opening area and depth.

The grinding apparatus or homogenized according to the invention is intended to grind larger, substantially lumpy or finely distributed and preferably loose and soft materials, for example species of stone, plants, types of grain, chemicals, foodstuffs, textiles, paper which are suspended (slurried) in gases, liquids or in solid finely distributed substances (carriers). As a result of the treatment in the grinding apparatus, the material ground is finely distributed and/or its surface structure is affected such, that certain valuable properties are effected. For example, by r-oughening the surface or the end portions of textile or paper fibers the binding and matting properties are improved.

The grinding apparatus according to the invention renders it further possible to change the grinding effect, i.e. the type of treatment carried out between the grinding surfaces, for example, slipping contra brushing (roughening) of fibrous materials.

The aforesaid improved grinding effect may be explained by the rapid changes in direction of flow of the material to be ground and further by the fact that there is a pressure wave in front of the grinding members on the way through the material to be ground and the carriers, by which pressure wave adjacent material to be ground which has less or no relative speed, is shaken or vibrated. The said vibration (which is sometimes called sound effect) is particularly strong when the grinding member passes over an opposite grinding member. The pressure wave may, however, even be increased in such a manner, that an adjacent co-rotary grinding member is placed angularly in relation to the line of action of the first mentioned grinding member, with the result that, due to interference, surges with specially high material vibrating effect are produced in the pressure wave.

Due to the rapid changes in the direction of its flow, all material to be ground is brought into intimate contact with the grinding surfaces, even in the cases when there is a relatively wide space between the said surfaces. It is, therefore, an advantage of the grinding apparatus according to the invention, that normally the grinding surfaces must not be placed at such a close distance to one another that, in the event of a sudden interruption of the material flow the two surfaces will become brazed or welded together.

The invention will be described in greater detail, reference being had to the accompanying drawings wherein:

FIG. 1 shows in a schematic manner and partially in section an embodiment of the grinding apparatus according to the invention with two disc-shaped grinding members having relative rotary movement wherein one member is stationary and the other member is rotatable.

FIG. 2 shows in a schematic manner and partially in section another embodiment of a grinding apparatus according to the invention with two rotating disc-shaped grinding members.

FIG. 3 shows in a schematic manner and partially in section a grinding apparatus according to the invention having one grinding member in the form of a truncated cone.

FIG. 4 shows in a schematic manner and partially in section a further embodiment of a grinding apparatus according tothe invention having a cylindrical grinding member.

FIG. shows in detail and in section two opposite grinding members in a grinding apparatus according to the invention.

FIG. 6 shows in detail and in section view another embodiment of two opposite grinding surfaces in a grinding apparatus according to the invention.

FIG. 7 shows in detail and partially in section a horizontal view of an embodiment of a flat grinding surface in a grinding apparatus according to the invention.

FIG. 8 shows in detail and partially in section a view of a further embodiment of two opposite grinding surfaces in a grinding apparatus according to the invention, and

FIG. 9, finally, is similar view to that of FIG. 8 but with the grinding member being of conical shape.

Referring to FIGS. 1-4, different types of grinding apparatus are shown with their grinding surfaces shaped according to the present invention. In FIG. 1, a stationary grinding surface 1 cooperates with a rotary grinding surface 2. The grinding surface 2 is driven in rotation by power sources 3, for example an electromotor. In FIG. 2 the grinding surfaces 1a, 2a are both driven in rotation by power sources 3a.

In FIG. 3 the surfaces are 112, 2b which are respectively constituted as the surface of a conical housing and the surface of a rotatable conical member supported in the housing and driven in rotation by power source 36.

In FIG. 4, the arrangement is similar to that in FIG. 3 with exception that the housing and the rotatable member are both cylindrical. The grinding surfaces are supported such that they are preferably adjustable relative one another. The rotary movement of the grinding surfaces relative one another can be effected in such a manner that one grinding surface is maintained stationary and the opposite one rotated, possibly with periodical changes of its direction or rotation. Both grinding surfaces may rotate, in which case the surfaces should preferably rotate in opposite directions, but it is even possible to rotate both surfaces in the same direction, in which case, of course, they must rotate at a different speed. In the last mentioned case, the material to be ground is treated very softly, thereby ensuring a rapid passage of the material between the grinding surfaces. Even in the latter cases, the direction of rotation may, of course, be changed.

FIG. 5 shows in detail and in section two opposite grinding surfaces 1d and 2d each provided with rows of depressions 4 and 5, the walls located to the side of the rows of depressions 4 and 5 forming elevations 6 and 7 projecting into opposite depressions 5 and 4 respectively. The walls 8 and 9 between the depressions 5 and 4 respectively in a row are provided with recesses 10 and 11 adjusted according to the elevations 6 and 7 respectively to accommodate the same.

In the embodiment of the grinding apparatus according to the invention shown in FIG. 6, the elevations 6a and 7a are elongated and provided with recesses in such a manner, that teeth 16 and 17 are formed. As a result thereof, the material to be ground can pass between the grinding surfaces, even when the elevations reach to the bottom of the opposite depressions. In certain cases it may be advantageous to place the teeth in a certain manner in relation to each other and to the teeth on the opposite grinding surface, for example in such a manner, that the material flow is blocked when the grinding surfaces are in a certain position relative one another. For

increasing the grinding effect, the depressions 4a and 5a are provided with holes 13 and 12 respectively, which holes may have any shape, for example circular, square or rectangular shape. The holes may have like or different shape, depth and opening area. The recesses in the elevations may be formed of different shape, so that the teeth may have, for example, square, rhombic, rectangular, circular or irregular cross-section. The teeth may also be provided with specially pointed edges.

When the grinding discs of FIG. 6 are axially movable in relation to one another and the grinding surfaces are moved to a position very close to one another, a cutting or crushing grinding effect is achieved, while with the surfaces spaced apart a greater distance the effect obtained will be that of a splitting or roughening nature.

FIG. 7 shows a horizontal view of a grinding surface of the type shown in FIG. 6 with depressions 5a wherein square holes 12 are disposed. The wall 7a to the side of a row of depressions 5a is elevated and shows regularly shaped teeth 17. The walls 8a between the depressions 5a are provided with recesses 10a for receiving the elevated Wall of an opposite grinding surface.

The grinding apparatus according to the invention may be provided with screwor wing-shaped feed means 14 (FIG. 5) or 14a (FIGS. 6 and 7) and/or discharge means 15 (FIG. 6).

A preferable embodiment of grinding surfaces in the grinding apparatus according to the invention is shown in FIG. 8. In this embodiment, the elevations 6 and 7a of the wall and the teeth 16b and 17b are tapered towards the free end. This construction is advantageous from a strength point of view and, additionally, renders possible a greater change in the grinding effect by displacing the grinding surfaces axially relative to another than obtained in the grinding apparatus according to FIG. 6.

FIG. 9, finally, illustrates grinding surfaces in a grinding apparatus according to the invention which have conical shape, the cone angle in the apparatus shown being The depressions in the grinding surfaces may preferably have a total cross-section area which is to 10 times the area of the feed opening, measured at one and the same distance from the center of the grinding apparatus at a right angle to the theoretical material flow. The cross-section area and the feed opening are however, preferably of like size. In view of wear, etc., the crosssection of a commercial grinding apparatus will during its lifetime vary considerably. For this reason, in a new grinding apparatus the section should be greater than the inlet area.

The grinding effect depends further on the concentration of the material in the carrier and on the relative speed of the grinding surfaces in relation to one another. According to the invention, all concentrations from 0 to as well as all relative speeds, even varying ones are applicable.

For illustrating the advantages of the invention, wet strong kraft paper was cut to pieces of one centimeter and suspended, to 3% concentration, in water from the city water supply of about 20 C. This suspension was fed into a disc grinding apparatus according to the invention with a disc diameter of about 60 mm. and 6000 r./m. (circumferential speed about 19 m./sec.). At an energy consumption of 1-2 kW.-h./ 100 kg. of paper and at a suitable distance between the grinding surfaces, complete decomposing (parting to individual fibers) was obtained after one pass of the suspension.

Commercial disc grinding apparatus which are said to be particularly suitable for this purpose have a disc diameter of about 280 mm. at 3000 r./m. (circumferential speed about 44 m./sec.) and have an energy consumption of 5-10 kw.-h./10O kg. of paper. For achieving complete decomposing under the same conditions, the

material must be passed more than twice through these apparatus. Consequently, the grinding apparatus according to the invention has the advantages of less energy consumption in combination with less wear.

What I claim is:

1. Grinding apparatus comprising a pair of members including spaced opposed surfaces, each of said surfaces being provided with depressions and bounding wall projections, the depressions and wall projections of respective surfaces being offset such that the wall projections of each surface project into corresponding depressions in the opposed surface, means supporting said members for rotation at different speeds about concentric axes such that the projections travel in said recesses, each wall projection being narrower than the corresponding depression to lie in spaced relation relative to the perimetral bounds of said depression, each member including lateral walls in said depressions dividing the latter into a plurality of compartments, said lateral walls being phovided with recesses to accommodate corresponding projections and permit passage thereof through said lateral walls upon relative roraty movement between the members.

2. Grinding apparatus as claimed in claim 1 wherein said surfaces are conical.

3. Grinding apparatus comprising a pair of members including spaced opposed surfaces, each of said surfaces being provided with at least one circularly extending depression, said surfaces including a Wall projection bounding said depressions, said depressions and wall projections of said surfaces being respectively offset such that the wall projection of each surface extends into the depression of the opposed surface, means supporting said members for rotation at different speeds about a common axis which is concentric with the depression such that the wall projections travel in the depressions, each of said members including lateral walls in said depressions dividing the latter into compartments, said lateral walls being recessed to permit passage therethrough of said wall projections upon relative rotary movement between the members.

4. Grinding apparatus as claimed in claim 3 wherein said wall projections are provided at least in part with slots.

5. Grinding apparatus as claimed in claim 3 wherein said depressions are bowl-shaped and the bounding wall projections narrow upwardly and are widest in a base portion.

6. Grinding apparatus as claimed in claim 3 wherein said surfaces extend perendicularly to the axis of rotation.

7. Grinding apparatus as claimed in claim 3 wherein said wall projections have a symmetrical cross section.

8. Grinding apparatus comprising a pair of members including spaced opposed surfaces, each of said surfaces being provided with at least one circularly extending depression, said surfaces including a Wall projection bounding said depressions, said depressions and wall portions of said surfaces being respectively offset such that the wall projection of each surface extends into the depression of the opposed surface, said members being adapted for being rotated relative to one another about an axis concentric with the depressions such that the wall projections travel in the depressions, each of said members including lateral walls in said depressions dividing the latter into compartments, said lateral walls being recessed to permit passage therethrough of said wall projections upon relative rotary movement between the members, said surfaces being provided with cavities opening into each of said depressions to face the corresponding wall projections, said cavities being arranged in spaced relation in a circular path concentric with said axis.

9. Grinding apparatus as claimed in claim 8 wherein said cavities are of square shape.

10. Grinding apparatus comprising spaced relatively movable members having opposed surfaces respectively including a projecting wall portion and an adjoining depression, said wall portions and adjoining depressions generally extending in the direction of relative movement of the members, the wall portion of one member being transversely offset from the wall portion of the other member such that the wall portion of each member is accommodated with clearance in the depression of the other member, each member including transverse projections extending from said wall portion thereof in a direction perpendicular to the direction of relative movement of the members into and across the adjoining depressions, the projections extending to a height less than that of the associated wall portion but beyond the wall portion of the other member which is accommodated in the depression such that the said transverse projections of said members face one another in proximate relation within each said depression.

11. Grinding apparatus as claimed in claim 10 wherein members are relatively movable about an axis of rotation, the transverse projections having proximate faces which are substantially perpendicular to the axis of rotation.

12. Grinding apparatus as claimed in claim 10 wherein said projections have spaced end portions permitting passage therebetween of part of the projecting wall portion received in the depression.

13. Grinding apparatus as claimed in claim 12 wherein said part of the projecting wall portion received between said spaced end portions of said projections is provided with slots extending radially of the axis of rotation to form teeth.

14. Grinding apparatus as claimed in claim 13 wherein the said slots have a base which lies between said spaced end portions of said projections.

References Cited by the Examiner UNITED STATES PATENTS 1,078,436 11/13 Hance 241-261 1,711,154 4/29 Michal 241-261 1,744,235 1/ 30 Markley et al. 241261 2,578,540 12/51 Gundlach 241236 2,623,700 12/52 Scherer 24126 1 WILLIAM W. DYER, JR., Primary Examiner.

EVERETT W. KIRBY, I. SPENCER OVERHOLSTER,

ANDREW R. JUHASZ, Examiners. 

1. GRINDING APPARATUS COMPRISING A PAIR OF MEMBERS INCLUDING SPACED OPPOSED SURFACES, EACH OF SAID SURFACES BEING PROVIDED WITH DEPRESSIONS AND BOUNDING WALL PROJECTIONS, THE DEPRESSIONS AND WALL PROJECTIONS OF RESPECTIVE SURFACES BEING OFFSET SUCH THAT THE WALL PROJECTIONS OF EACH SURFACE PROJECT INTO CORRESPONDING DEPRESSIONS IN THE OPPOSED SURFACE, MEANS SUPPORTING SAID MEMBERS OF ROTATION AT DIFFERENT SPEEDS ABOUT CONCENTRIC AXES SUCH THAT THE PROJECTIONS TRAVEL IN SAID RECESSES, EACH WALL PROJECTION BEING NARROWER THAN THE CORRESPONDING DEPRESSION TO LIE IN SPACED RELATION RELATIVE TO THE PERIMETRAL BOUNDS OF SAID DEPRESSION, EACH MEMBER INCLUDING LATERAL WALLS IN SAID DEPRESSIONS DIVIDING THE LATTER INTO A PLURALITY OF COMPARTMENTS, SAID LATERAL WALLS BEING PHOVIDED WITH RECESSES TO ACCOMMODATE CORRESPONDING PROJECTIONS AND PERMIT PASSAGE THEREOF THROUGH SAID LATERAL WALLS UPON RELATIVE RORATY MOVEMENT BETWEEN THE MEMBERS. 